“Metallic” and “Insulating” Behavior of the Two-Dimensional Electron Gas on a Vicinal Surface of Si MOSFET's

The resistance R of the 2DEG on the vicinal Si surface shows unusual behavior which is very different from that in Si (100) MOSFET's studied earlier. The low-temperature crossover from dR/dT<0 ("insulator") to dR/dT>0 ("metal") occurs at a low resistance of R(c)square approximately 0.04xh/e2. This crossover, which we attribute to the existence of a narrow impurity band at the interface, is accompanied by a distinct hysteresis in the resistance. At higher temperatures, another change in the sign of dR/dT is seen. We describe it by temperature dependent impurity scattering of the 2DEG near the transition from the degenerate to nondegenerate state.